Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0011849 (diabetes)
 277,896 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A 6-yr-old boy presented with muscle weakness, lactic acidemia, and insulin-dependent diabetes mellitus (IDDM). Using PCR and restriction enzyme analysis, he was found to have the classical A3248G mitochondrial DNA (mtDNA) mutation frequently associated with mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS). The mutation was confirmed by sequencing muscle mtDNA. The mutation in mtDNA from muscle, lymphoblasts, and blood was clearly demonstrable by standard methods using ethidium bromide staining. His mother also had IDDM, but no A3243G mutation could be detected in her blood or transformed lymphoblasts using the same PCR technique. When PCR was carried out in the presence of [32P]deoxycytidine triphosphate, subsequent autoradiography detected the presence of the mutation at low levels in mtDNA from the mother's lymphoblasts and blood. Study of the mother's muscle showed a mitochondrial myopathy, despite the fact that she was asymptomatic. We emphasize that the increased sensitivity of radiolabeled PCR may be necessary to detect small percentages of heteroplasmic A3243G mtDNA mutation in blood from diabetic subjects. Otherwise the incidence of mtDNA mutations in both IDDM and non-insulin dependent diabetes may be underestimated.
 ...
PMID:Diabetes and mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS): radiolabeled polymerase chain reaction is necessary for accurate detection of low percentages of mutation. 928 4

Treatment of the rat ovarian membrane-bound and Triton X-100 solubilized LH/hCG receptor with the tryptophan-specific reagents N-bromosuccinimide (NBS) and 2-hydroxy-5-nitrobenzyl bromide (HNB-Br) resulted in inactivation of the receptor to bind hCG. Fluorescence quenching studies indicated that oxidation of tryptophan residues by NBS decreased the accessibility of fluorophores for acrylamide. Preceding binding of hCG to receptor sites was found to protect fluorophores from NBS action. Modification of tryptophan residues was associated with alteration in the rigidity of ovarian membranes and with destabilization of the LH/hCG receptor structure. The results suggest that tryptophan residue is essential for hCG binding to the receptor.
Exp Clin Endocrinol Diabetes 1997
PMID:Involvement of tryptophan in the structural alterations of the rat ovarian LH/hCG receptor. 935 60

Mitochondrial dysfunction due to alterations in the mitochondrial genome (mtDNA) has recently attracted much attention, with the finding that mutations in the mitochondrially encoded proteins perturb cell function. Several disorders have been linked to such genetic changes, including a specific diabetic phenotype. Using ethidium bromide (EtBr) that intercalates into mtDNA, we have effectively eliminated functions under the control of mtDNA from the highly differentiated INS-1 insulin-secreting cell line. We have investigated the consequences on insulin secretion, mitochondrial enzyme activity, organelle structure, and membrane polarization in such cells (INS-1 rho0). Under these conditions, the mitochondrial membrane potential fails to hyperpolarize in response to either glucose or methylsuccinate. In agreement with this finding, the morphology of the mitochondria is altered in the presence of EtBr, sharing similarities with mitochondria in which the membrane potential has been collapsed with the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone (FCCP). In addition, there is no effect of either nutrient secretagogue at the level of the plasma membrane potential, although the effect of the depolarizing agent KCl on membrane depolarization is completely preserved. Similarly, glucose and methylsuccinate fail to increase insulin secretion, whereas KCl is still effective. To test further the effects of mtDNA depletion on exocytosis, we permeabilized INS-1 cells with Staphylococcus aureus alpha-toxin, which forms small holes in the plasma membrane. In contrast to control cells, mitochondrial substrates were incapable of stimulating insulin secretion in mtDNA-deficient cells, emphasizing that the defect in secretion lies at the level of mitochondrial function rather than in the exocytotic process. The results indicate the paramount importance of the mitochondria in the downstream effects elicited by exposure to elevated concentrations of nutrient secretagogue.
Diabetes 1998 Mar
PMID:Effects of depletion of mitochondrial DNA in metabolism secretion coupling in INS-1 cells. 951 42

It has been proposed that mitochondrial oxidative phosphorylation in pancreatic beta-cells plays an important role in insulin secretion. To examine the impact of mitochondrial dysfunction on insulin secretion, we created a MIN6 cell line that depleted mitochondrial DNA (mtDNA) by treatment with ethidium bromide (EtBr), and studied the response of the cell line to various secretagogues. MIN6 cells cultured with 0.5 microg/ml EtBr for over 2 months (termed MIN6 deltamt cells) revealed a marked (>90%) decrease in mtDNA content and a lack of mRNAs encoded by mtDNA. MIN6 deltamt cells showed the defects of cytochrome c oxidase activity, glucose- and leucine-induced increase in cellular ATP content, and respiratory chain-driven ATP synthesis, suggesting that MIN6 deltamt cells lost oxidative phosphorylation activity due to the selective disruption of the subunits of respiratory chain enzymes encoded by mtDNA. MIN6 deltamt cells also showed a decrease in glucose utilization, suggesting the impairment of the glycolytic pathway as well. After stimulation with glucose and leucine, MIN6 deltamt cells showed no response in insulin secretion or intracellular free Ca2+ concentration ([Ca2+]i). On the other hand, arginine stimulated insulin secretion and an increase in [Ca2+]i in MIN6 deltamt cells as in MIN6 cells. Glibenclamide also stimulated insulin secretion and an increase in [Ca2+]i in both types of cells, but the responses of MIN6 deltamt cells were significantly lower than those of MIN6 cells. These results suggest the importance of ATP production in insulin secretion and an increase in [Ca2+]i, both induced by glucose and leucine. Moreover, mitochondrial function turns out to be not essential but important for the activation of sulfonylurea-induced insulin secretion.
Diabetes 1998 Apr
PMID:Creation and characterization of a mitochondrial DNA-depleted pancreatic beta-cell line: impaired insulin secretion induced by glucose, leucine, and sulfonylureas. 956 96

The present study investigates the role of metal catalysed oxidation in the formation of Advanced Glycation End products (AGEs). Rat tail tendon collagen was incubated with glucose (250 mM) and increasing concentrations of copper ions (5-500 microM) under physiological conditions of temperature and pH. After 1 and 3 weeks of incubation the level of AGEs in collagen samples were estimated by enzyme linked immunoassay, using antibodies raised against AGE ribonuclease. It was observed that the presence of metal ions significantly increased the rate of accumulation of AGEs. The increase was dependent on the concentration of metal ions present in the incubation medium. Free radical scavengers such as mannitol, benzoate, catalase, and the antiglycating agent aminoguanidine almost completely inhibited the formation of AGEs. Incubation of collagen with copper ions alone did not show any increase in crosslinking, as detected by cyanogen bromide digestion, and AGEs formation. Further it was also noted that glycoxidation, i.e., oxidation of glycated collagen, was the major pathway that leads to increased formation of AGEs. These results indicate that metal-catalyzed oxidation and free radicals play a major role in the formation of AGEs. This work also strongly suggests that increased oxidative stress in diabetes may accelerate the formation of AGEs and thus contribute to the pathogenesis of diabetic complications.
 ...
PMID:The role of metal-catalyzed oxidation in the formation of advanced glycation end products: an in vitro study on collagen. 968 Jan 71

Recently, a mitochondrial mutation was found to be associated with maternally inherited diabetes mellitus (Kadowaki, T., Kadowaki, H., Mori, Y., Tobe, K., Sakuta, R., Suzuki, Y., Tanabe, Y, Sakura, H., Awata, T., Goto, Y., Hayakawa, T., Matsuoka, K., Kawamori, R., Kamada, T., Horai, S., Nonaka, I., Hagura, R., Akanuma, Y., and Yazaki, Y. (1994) N. Engl. J. Med. 330, 962-968). In order to elucidate its etiology, we have investigated the involvement of mitochondrial function in insulin secretion. Culture of the pancreatic beta-cell line, betaHC9, with low dose ethidium bromide (EB) (0.4 microg/ml) for 2-6 days resulted in a substantial decrease in the transcription level of mitochondrial DNA (to 10-20% of the control cells) without changing its copy number, whereas the transcription of nuclear genes was grossly unaffected. Electron microscopic analysis revealed that treatment by EB caused morphological changes only in mitochondria and not in other organelles such as nuclei, endoplasmic reticula, Golgi bodies, or secretory granules. When the cells were treated with EB for 6 days, glucose (20 mM) could no longer stimulate insulin secretion, while glibenclamide (1 microM) still did. When EB was removed after 3- or 6-day treatment, mitochondrial gene transcription recovered within 2 days, and the profiles of insulin secretion returned to normal within 7 days. Studies with fura-2 indicated that in EB-treated cells, glucose (20 mM) failed to increase intracellular Ca2+, while the effect of glibenclamide (1 microM) was maintained. Our system provides a unique way to investigate the relationship between mitochondrial function and insulin secretion.
 ...
PMID:Ethidium bromide-induced inhibition of mitochondrial gene transcription suppresses glucose-stimulated insulin release in the mouse pancreatic beta-cell line betaHC9. 968 80

We have investigated the effect of advanced glycation end products (AGEs) on the crosslinking of collagen. The potential pathological significance of AGEs and the altered metabolism of ascorbic acid (ASA) in diabetes have prompted us to investigate the role of ASA in the crosslinking and advanced glycation of collagen. Rat tail tendons were incubated with ASA and dehydroascorbic acid (DHA) under physiological conditions of temperature and pH, and the crosslinking and the level of AGEs were analyzed. Analysis of crosslinking was conducted by pepsin solubility and cyanogen bromide digestion. Level of AGEs was estimated by enzyme-linked immunosorbent assay (ELISA) using antibodies raised against AGE-ribonuclease. It was noted that ASA and DHA induced crosslinking of collagen and stimulated the formation of AGEs. It was also noted that these pathways were dependent on oxidative conditions. Similarly incubation of collagen with AGEs, prepared by the in vitro incubation of bovine serum albumin (BSA) with glucose, also resulted in increased crosslinking. The extent of crosslinking was dependent on the duration of incubation. The novel finding of this study, which is in contrast to the earlier reports on glucose-induced crosslinking of collagen, was that AGEs-induced crosslinking of collagen was not inhibited by radical scavengers and the metal chelator. EDTA, whereas glucose-induced crosslinking of collagen was almost completely prevented by free radical scavengers. The increased fluorescence intensity observed in collagen incubated with AGEs was also not prevented by radical scavengers. Estimation of AGEs by ELISA revealed an increased accumulation of AGEs in collagen incubated with AGE-BSA. The inhibitory effect of aminoguanidine and aspirin on AGEs-induced modification of collagen, strongly suggests that the amino-carbonyl interaction between AGEs and collagen may play a key role in the crosslinking process. The results obtained in this study indicate that soluble AGEs can directly induce crosslinking of collagen and this process is independent of oxidative conditions. From these results it may be hypothesized that glucose, under oxidative conditions, reacts with proteins to form potentially reactive end products called AGEs. These AGEs, once formed, could induce crosslinking of collagen even in the absence of both glucose and oxygen.
 ...
PMID:Advanced glycation end products induce crosslinking of collagen in vitro. 974 85

The present investigation was carried out to understand the effect of metal catalyzed oxidation on glycation and crosslinking of collagen. Tail tendons obtained from rats weighing 200-225 g were incubated with glucose (250 mM) and increasing concentrations of copper ions (5, 25, 50 and 100 microM) under physiological conditions of temperature and pH. Early glycation, crosslinking and late glycation (fluorescence) of collagen samples were analyzed periodically. Early glycation was estimated by phenol sulfuric acid method, and the crosslinking was assessed by pepsin and cyanogen bromide digestion. A concentration-dependent effect of metal ions on the rate of glycation and crosslinking of collagen was observed. Tendon collagen incubated with glucose and 100 microM copper ions showed 80% reduction in pepsin digestion within seven days, indicating extensive crosslinking, whereas collagen incubated with glucose alone for the same period showed only 7% reduction. The presence of metal ions in the incubation medium accelerated the development of Maillard reaction fluorescence on collagen, and the increase was dependent on the concentration of metal ions used. The metal chelator diethylene triamine penta-acetate significantly prevented the increase in collagen crosslinking by glucose and copper ions. Free radical scavengers benzoate and mannitol effectively prevented the increased crosslinking and browning of collagen by glucose. The results indicate that the metal catalyzed oxidation reactions play a major role in the crosslinking of collagen by glucose. It is also suggested that the prevention of increased oxidative stress in diabetes may prevent the accelerated advanced glycation and crosslinking of collagen.
 ...
PMID:An in vitro study on the role of metal catalyzed oxidation in glycation and crosslinking of collagen. 1039 Nov 48

A mitochondrial DNA (mtDNA) point mutation at nucleotide pair (np) 3316 has been reported in relation to diabetes. We recently encountered a non-obese family with this type of mutation. The proband in the affected family, a 49-year-old woman who had been previously diagnosed as having an insulin-requiring non-insulin-dependent diabetes mellitus (NIDDM), was referred to our hospital for treatment of diabetic gangrene in her left foot. Her insulin secretory capacity was markedly reduced, but the insulin sensitivity evaluated by the euglycemic hyperinsulinemic clamp technique was normal. In addition, her serum lactate level was markedly increased after a 5 min ambulation, although her serum pyruvate and ketones remained within the normal range. Twenty-year-old twin sons had been treated with insulin since the age of 7, when both were diagnosed with insulin-dependent diabetes mellitus (IDDM). The proband's mother, a 68-year-old, was nondiabetic at this time. MtDNA analysis revealed a point mutation at np 3316 in all family members, which was homoplasmic for the mutation on a photograph of agarose gel electrophoresis containing ethidium bromide under ultraviolet light. This mutation seemed to be maternally transmitted in the family, and the onset of diabetes was occurring earlier and the insulin secretory capacity was declining from generation to generation, so that these findings suggest that the point mutation at np 3316 is associated with various phenotypes of diabetes.
 ...
PMID:Mitochondrial DNA point mutation at nucleotide pair 3316 in a Japanese family with heterogeneous phenotypes of diabetes. 1039 42

Dicarbonyl-containing compounds such as methylglyoxal (MG) are toxic to cells since they can interact with the nucleophilic centers of macromolecules. MG has been found to accumulate during hyperglycemia, and it has been suggested that this reactive dicarbonyl may contribute to the tissue damage and long-term complications of diabetes. A sensitive bacterial assay for investigating the ability of nucleophilic agents to interact with and detoxify MG has been developed. This assay utilizes the sensitivity of exponential phase cells of an Escherichia coli double mutant lacking the KefB and KefC potassium channels toward MG. The bidentate nucleophile, phenylacylthiazolium bromide (PTB), was found to protect and allow the growth of E. coli cells in the presence of either externally added or endogenously produced MG. In the absence of PTB, growth was completely inhibited and rapid cell death occurred under these conditions. PTB protected E. coli against MG almost as well as aminoguanidine, a compound shown previously to be involved in detoxification. The level of protection by PTB against MG was much greater than for the endogenous nucleophile, glutathione. These data suggested that PTB could interact with and detoxify MG. The mechanism of this interaction was characterized by NMR and mass spectroscopy.
 ...
PMID:Detoxification of methylglyoxal by the nucleophilic bidentate, phenylacylthiazolium bromide. 1040 1


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>